U.S. patent number 4,296,996 [Application Number 06/058,251] was granted by the patent office on 1981-10-27 for feedthrough for optical fiber.
This patent grant is currently assigned to Kokusai Denshin Denwa Kabushiki Kaisha. Invention is credited to Kahei Furusawa, Yasuhiko Niiro, Akira Okada.
United States Patent |
4,296,996 |
Niiro , et al. |
October 27, 1981 |
**Please see images for:
( Certificate of Correction ) ** |
Feedthrough for optical fiber
Abstract
An optical fiber feedthrough for an optical submerged repeater
for use in an optical fiber submarine cable, in which a metal film
is coated on the outer peripheral surface of an optical fiber to be
introduced into the repeater, and in which a thermoplastic
material, such as polyethylene or the like, is filled between the
inner wall of a hole made in an end face plate of a pressure
resisting container of the repeater and the metal film.
Inventors: |
Niiro; Yasuhiko (Yokohama,
JP), Furusawa; Kahei (Kamifukuoka, JP),
Okada; Akira (Tokyo, JP) |
Assignee: |
Kokusai Denshin Denwa Kabushiki
Kaisha (Tokyo, JP)
|
Family
ID: |
13895048 |
Appl.
No.: |
06/058,251 |
Filed: |
July 17, 1979 |
Foreign Application Priority Data
|
|
|
|
|
Jul 18, 1978 [JP] |
|
|
53-86734 |
|
Current U.S.
Class: |
385/138;
174/70S |
Current CPC
Class: |
G02B
6/4428 (20130101) |
Current International
Class: |
G02B
6/44 (20060101); G02B 007/26 () |
Field of
Search: |
;350/96.20,96.21,96.23,96.30,96.33 ;174/7S
;427/162,163,166,168 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2721347 |
|
Nov 1978 |
|
DE |
|
2000390 |
|
Jan 1979 |
|
GB |
|
2003294 |
|
Mar 1979 |
|
GB |
|
Other References
Pinnow et al., "Reductions In Static Fatigue . . .", Appl. Phys.
Lett., vol. 34, No. 1, Jan. 1979, pp. 17-19. .
Almeida et al., "On Line-Metal Coating of Optical Fibres", Optik,
vol. 53, No. 3, Jun. 1979, pp. 231-233..
|
Primary Examiner: Lee; John D.
Attorney, Agent or Firm: Burns; Robert E. Lobato; Emmanuel
J. Adams; Bruce L.
Claims
What we claim is:
1. In a submarine repeater, a pressure-resisting solid container
having a feed-through opening for receiving an optical fiber, an
optical fiber extending longitudinally through said opening, a
sealing thermoplastic material filling space between the fiber and
inner surfaces of said through opening in said pressure-resisting
solid container, said optical fiber having a metallic film coating
circumferentially and longitudinally thereon in close contact with
said sealing thermoplastic material to ensure a seal having
resistance to high fluid pressure and airtightness between the
optical fiber and said thermoplastic material, said metallic film
coating having an oxide film thereon to provide enhanced sealing
close contact between the metallic film coating and the
thermoplastic material.
2. In a submarine repeater according to claim 1, in which said
metallic film coating is thickened in an area defining a
collar-like enlargement circumferentially of the optical fiber,
said feedthrough opening having a large inner diameter in an axial
portion thereof to accommodate said enlargement thereby to prevent
longitudinal displacement of said optical fiber.
3. In a submarine repeater according to claim 1, including a
metallic ring on said optical fiber circumferentially thereof for
precluding longitudinal displacement of said optical fiber, said
feedthrough opening having an enlarged inner diameter in an axial
portion thereof to accommodate said ring thereby to preclude said
longitudinal displacement of the optical fiber.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a feedthrough of an optical submerged
repeater used in a long-distance, optical-fiber submarine cable
system in the field of optical communication employing a low-loss
optical fiber.
2. Description of the Prior Art
An optical submerged repeater is laid in the sea at a depth of
several thousand meters and exposed to a water pressure of several
hundred atmospheric pressures; therefore, optical and electronic
circuits of the optical submerged repeater are housed in a pressure
resisting container made of a material of high durability against
seawater, for example, stainless steel or beryllium copper. The
optical and electronic circuits in the pressure resisting container
and an optical-fiber submarine cable are interconnected via a
feedthrough attached to an end face plate of the pressure resisting
container to serve as an introducing part for an optical fiber and
a power feeding conductor. The pressure in the pressure resisting
container is usually 0 to 1 atmospheric pressures in terms of gauge
pressure and a pressure difference between the inside and outside
of the pressure resisting container is very large. Accordingly, the
feedthrough is required to have a construction which withstands a
high pressure while retaining a high degree of airtightness.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical fiber
feedthrough for interconnecting an optical circuit in the pressure
resisting container to an external optical-fiber submarine
cable.
The optical fiber feedthrough of this invention is required to
satisfy the following requirements:
The feedthrough:
(1) Has a high degree of airtightness which prevents seawater from
entering into the pressure resisting container through the optical
fiber feedthrough in the sea at a depth of about ten thousand
meters;
(2) Has a high pressure resisting construction which prevents that
a non-uniform force is applied to the optical fiber in the
feedthrough to bend or break the optical fiber; and
(3) Satisfies the above conditions (1) and (2) over as long a
period as more than twenty years.
This invention is intended to materialize an optical fiber
feedthrough which satisfies such requirements as mentioned above
and in which the outer peripheral surface of a cladding of an
optical fiber, which is weak mechanically, is coated with a metal
to provide for an increased mechanical strength of the optical
fiber against a tensile force or an external force, and in which
close contact between the optical fiber and the metal coating is
ensured by the long entire length of the coating so that close
contact between the metal coating and polyethylene or like
thermoplastic material inserted between the coating and an end face
plate of a pressure resisting container is enhanced by forming an
oxide film on the surface of the metal coating or by increasing the
thickness of a part of the metal coating, thereby to ensure high
pressure resistance and a high degree of airtightness of the
feedthrough.
BRIEF DESCRIPTION OF THE DRAWING
This invention will be hereinafter described in detail with
reference to the accompanying drawing, in which:
FIG. 1A is a longitudinal sectional view of an embodiment of this
invention;
FIG. 1B is a perspective view illustrating the principal part of
the embodiment of FIG. 1A;
FIG. 2A is a longitudinal sectional view illustrating another
embodiment of this invention;
FIG. 2B is a perspective view showing the principal part of the
embodiment of FIG. 2A;
FIG. 3A is a longitudinal sectional view illustrating a further
embodiment of this invention; and
FIG. 3B is a perspective view showing the principal part of the
embodiment of FIG. 3A.
DETAILED DESCRIPTION
FIG. 1A is a sectional view of an embodiment of this invention,
showing an optical fiber feedthrough attached to a part of an end
face plate of a pressure resisting container. The outside and
inside of the pressure resisting container are indicated by A and
B, respectively. FIG. 1B illustrates in perspective an optical
fiber feedthrough unit which is inserted into a feedthrough unit
receiving hole 4a made in an end face plate 4. In FIGS. 1A and 1B,
reference numeral 1 indicates an optical fiber and 2 designates a
copper or like metal thin film coated around a cladding of the
optical fiber by which this invention is characterized; the metal
film 2 can easily be deposited by sputtering or ion plating on
glass. The metal film 2 can also be formed by non-electrolytic
plating. Further, it is also possible that the metal film 2 closely
formed by sputtering or ion plating around the optical fiber 1 is
made thicker by means of plating or that two layers of different
metals are deposited to different thicknesses. Thus, various
methods can be employed for forming the metal film 2 around the
optical fiber 1 and a metal of a desired thickness can easily be
coated closely around the optical fiber 1.
The optical fiber 1 given the metal coating by such method as
described above is further enclosed in a structure of a
thermoplastic material 3, such as polyethylene or the like, to
provide an optical fiber feedthrough unit, as shown in FIG. 1B, and
the feedthrough unit is inserted into the hole 4a made in the end
face plate 4 and is then fixed by a metal fitting 8. The structure
3 is formed of polyethylene or a like thermoplastic material. After
an oxide film is formed on the surface of the metal coating 2 to
achieve close contact between it and the polyethylene material,
polyethylene or a like material is formed to conform to the hole 4a
of the end face plate 4. This can easily be done by molding or the
like. The structure thus obtained is inserted into the hole 4a of
the end face plate 4 and fixed therein by the metal fitting 8, by
which can be obtained a feedthrough of high pressure resistance and
high airtightness.
Another example of the feedthrough can be obtained as follows: An
optical fiber coated with a metal is inserted into the hole 4a of
the end face plate 4 and then the part of the hole 4a of the end
face plate 4 is formed by molding so that the metal film 2 is in
close contact with the polyethylene structure 3, thereby to fix the
metal coated film and the polyethylene structure 3 relative to each
other.
FIGS. 2A and 2B show another example in which the metal coating of
the optical fiber is formed thick at one or more parts to provide
thick portions 7 for providing for improved close contact of the
metal coating with the polyethylene mold 3, thereby preventing
displacement of the optical fiber in a vertical direction.
FIGS. 3A and 3B illustrate another example, in which a ring-shape
metal 5 is mounted by brazing on the metal coating 2, as indicated
by numeral 6, and molded as a unitary structure with the
polyethylene structure 3 so as to provide for improved close
contact between the metal coating of the optical fiber and the
polyethylene molding 3 and enhanced pressure resistance.
The outer diameter of the optical fiber is as small as 100 to 200
.mu.m, whereas the metal coating is as thin as several to a few
dozen .mu.m and its outer diameter is as small as 300 to 500 .mu.m;
in contrast thereto, the feedthrough is as long as several cm
compared with its diameter. Therefore, such simple structure as
shown in the foregoing examples achieve sufficient reliability for
a long use.
The present invention has the following advantages:
(1) By forming the metal film in close contact with the optical
fiber of low mechanical strength, the mechanical strength of the
optical fiber against a tensile force and an external force can be
increased.
(2) The optical fiber made of a glass material and the metal
coating are well in close contact with each other and a high degree
of close contact required can be ensured by increasing the length
of the metal film of the optical fiber in its lengthwise direction,
so that a feedthrough of good airtightness can be obtained.
(3) A space between the optical fiber coated with metal and the
inner wall of a hole made in the end face plate for passing through
the optical fiber is filled with polyethylene or a like
thermoplastic material by means of molding, by which it is possible
to provide a feedthrough easy to manufacture.
(4) To improve the close contact between the metal coating and the
thermoplastic material structure, a ring-shaped metal is mounted by
brazing on the metal coating or the coating is formed thick partly,
by which it is possible to obtain a feedthrough easy to produce and
of high reliability.
* * * * *